In the high volume manufacture of many consumer products, the product housing, whether manufactured of plastic or metal, is formed of two or more parts. These parts, for example, the front and back of a radio housing, a cellular phone housing, a battery pack housing, or a floppy diskette, to name a few, have traditionally been joined together by processes such as gluing or ultrasonic welding. Gluing parts together by using an epoxy type glue has the disadvantage of being a relatively slow process as compared to the overall speed of current manufacturing processes. Moreover, the curing time for the epoxy is relatively long, during which period the front and back housings may not stay properly aligned. Accordingly, other processes such as ultrasonic or conventional welding of parts together has found an increasing acceptance in the marketplace. Ultrasonic welding is a process for using high speed vibration to melt localized areas, thus joining, for example, two pieces of plastic. Ultrasonic welding is not free from problems. In instances in which high volume products, e.g., on the order of 20 million units per year or more are being manufactured, housing parts such as those described above are typically ordered from at least two or more different suppliers. These suppliers manufacture the parts to a specification, and although manufactured to the same specifications, they have variations within tolerance limits that require adjustments to the setup of conventional ultrasonic welding devices. Typically, the time involved for setting up an ultrasonic welding station to accept a similar piece part from a different manufacturer can run on the order of 30-60 minutes, requiring substantial engineering effort to appropriately calibrate the device. Moreover, during the setup process, numerous piece parts are run on the device in order to check the quality of the device. Accordingly, hundreds and even thousands of piece parts may be scraped as a result of the set up process. The costs both in terms of time and scrap material are increasingly becoming unacceptable to most manufacturers.
Accordingly, there is a need for a self-leveling fixture for use in the manufacturing process such as an ultrasonic welding process. The self-leveling fixture should be provided so as to accommodate for subtle changes in the specification and tolerances of similar parts. This self-leveling fixture should allow for little or no variation in the presentation of the piece parts to be operated upon from the perspective of the operating device. Moreover, the self-leveling fixture should be easy to install and require little or no calibration.